The present invention relates to electronic circuits with ferroelectric flip-flops which can use arriving signals as the sole energy source, a liquid counter based on such an electronic circuit, a method for storing information contained in signals, and also the use of ferroelectric flip-flops for electronic circuits.
In conventional electronic circuits for processing signals, for example counting pulses, a supply voltage is required which supplies the logic modules. This supply voltage is supplied for example by a battery, such as a lithium battery. A battery considerably increases the production and operating costs of an apparatus which uses the circuit, and, moreover, has to be replaced at regular intervals. If results of a signal evaluation are to remain stored even when the operating voltage fails, a nonvolatile memory, for example EEPROM or FLASH-EPROM, is additionally required. Such electrically erasable memory cells require high voltages of minus 12 and plus 16 volts, respectively, for programming and for erasing, which have to be generated from the battery voltage by charge pumps. The relatively poor efficiency in high-voltage generation leads to a high power loss. Furthermore, EEPROM memories have a service life which is limited by the number of reprogramming processes. This is disadvantageous particularly in the case of counting circuits, where the so-called xe2x80x9cLeast Significant Bitxe2x80x9d (the bit which is least significant or the smallest position of the counter) has to be reprogrammed for each counting pulse that arrives.
Particularly in the case of apparatuses which are intended to be in operation over relatively long periods of time and/or at remote sites of use, the dependence on a supply voltage leads, moreover, to a significantly increased outlay on maintenance, since maintenance personnel have to go to the apparatuses especially for the purpose of exchanging the battery or monitoring the battery.
The use of a supply voltage generated from the electricity supply system is likewise associated with a high outlay and, in the case of remote sites, is in some instances not practicable at all. In the event of system failures, moreover, it may lead to incorrect counting results.
On account of the abovementioned disadvantages, however, there is a need to realize circuits which can operate as far as possible independently of the various voltage supplies mentioned above.
Consequently, the present invention is based on the object of providing a signal-processing and/or information-storing circuit which can be operated autonomously of external power supplies.
The present invention achieves this object by the provision of an electronic circuit in accordance with the independent patent claim 1, a method for information storage in accordance with the independent patent claim 16, the use of ferroelectric flip-flops for electronic circuits in accordance with the independent patent claim 22, and the liquid counter in accordance with the independent patent claim 26. Further advantageous configurations, details and aspects of the present invention emerge from the dependent patent Claims, the description and the accompanying drawings.
In the analysis of signal-processing circuits and the signal-generating sensors assigned thereto, it has now been found that although the energy inherent in the signals does not suffice to be able to operate EEPROM memories, this energy nonetheless still amounts to 30 nJ in the case of a typical pulse wire sensor. It has unexpectedly been found that this quantity of energy suffices to operate circuits if special flip-flops with implemented ferroelectric storage capacitances, so-called ferro-flip-flops, are used.
The present invention is therefore directed at an electronic circuit, having
an input for inputting at least one information signal; an energy means for converting energy contained in the at least one information signal into a voltage supply; a control means for generating at least one switch-on control signal when an information signal arrives; and a signal processing means for storing an information item represented by the at least one information signal and/or for evaluating an information item represented by the at least one information signal and storing the secondary information obtained through the evaluation by means of at least one ferroelectric flip-flop;
wherein the signal processing means can be activated by the at least one switch-on control signal for the purpose of evaluation and/or storage;
and wherein, during the evaluation and/or storage, the at least one information signal may be or is the sole energy source for the electronic circuit.
The electronic circuit according to the invention can thus also be provided with an external voltage supply. What is crucial, however, is that it does not rely on the latter for the information signal acquisition operation. Even in the event of a power failure, the electronic circuit according to the invention can continue to carry out its function. With regard to the power supply, the electronic circuit can thus be understood as a fail safe circuit. In particular embodiments and particularly preferred embodiments of the present invention, however, the electronic circuit is not actually provided with an external power supply, in so far as the latter is not connected for the readout of the stored information.
The ferroelectric flip-flops used according to the invention will be described in detail further below. In principle, they have the same structure as conventional flip-flops, that is to say they have, in particular a SET and a RESET input, and also a QB and Q output and NAND or NOR gates for the circuit logic. However, they are additionally provided with ferroelectric capacitors which enable them to store the logic state of the flip-flop when the voltage supply is disconnected and to reestablish the stored state when the voltage supply is switched on. For storing or reestablishing the state of the ferroelectric flip-flop, control signals are given in a temporally exact defined sequence (see below). Nonvolatile memories based on ferroelectric capacitors can be operated at low voltages and require only about a hundredth of the energy of EEPROM memories. In the case of the electronic circuit according to the invention, therefore, it is possible for the energy (10 nJ to 100 nJ) required for operating a customary circuit to be drawn solely from the arriving pulse or the arriving pulses.
Thus, according to the invention, the control means must be able to generate one or more control signals in a temporally controlled sequence and feed them to the signal processing means. This aim can be achieved in a simple manner using circuits and methods, respectively, known to persons skilled in the art. By way of example, different temporally staggered signals can be achieved by means of a bandgap difference circuit with a comparator circuit.
In the sense of the present invention, evaluation is to be understood as any interpretation of an information signal that has arrived by the signal processing means, for example the ascertainment of a time interval with respect to a preceding information signal, the logical combination via AND, OR, NAND, and NOR of different information signals, the counting up and down of information signals that arrive successively, and the toggling between on and off for successive arrivals of information signals, and any other conceivable interpretation of arriving information signals. In the sense of the present invention, a represented information item is to be understood to be any meaning which can be attributed to the input of an information signal in the temporal progression in its specific instance and in its relationship with other information signals.
The arriving information signals may have been generated by a customary sensor, for example. These are preferably sensors which generate a signal with a suitable voltage and with a sufficient energy content to be able to operate the circuit according to the invention. By way of example, inductive or piezoelectric sensors can be used. One possibility for a sensor that can be used is a pulse wire sensor, in which an external magnetic field, for example from a rotor provided with magnets, acts on a composite wire and generates therein an electrical pulse which is then available as information signal. In this case, the entire energy that is required is drawn from the magnetic field, so that an external energy supply is also not necessary for the sensor.
The electronic circuit according to the invention is preferably characterized in that the control means can generate at least one switch-off control signal after a predetermined time has elapsed after the at least one information signal arrives and/or when the energy converted from the at least one information signal is exhausted, wherein the signal processing means can be caused or is caused to effect a storage and to effect deactivation by the at least one switch-off control signal.
It is understood that a switch-off control signal is to be generated after time has elapsed only when, after the arrival of an information signal, no further information signal has arrived. The elapsing of a predetermined time thus always relates to the elapsing after the inputting of the last information signal, if a plurality of information signals have arrived successively. If the switch-off control signal is generated when the existing energy is exhausted, it is necessary to provide a circuit in the control means which can reliably ascertain that said energy is exhausted. By way of example, it is possible to use a circuit which can detect a possible voltage drop.
Preferably, the information stored in the at least one ferroelectric flip-flop can be converted into at least one output signal by the signal processing means, wherein in this case the electronic circuit furthermore has at least one output for outputting the at least one output signal. In this way, the information stored in the circuit can be read out again by a suitable read-out means.
The electronic circuit may furthermore have a display means for displaying the information stored in the at least one ferroelectric flip-flop. Such an additional display means is possible when sufficient energy for operating it can be obtained from the information signal. A display means enables the information stored in the at least one flip-flop to be read at any time.
Preferably, the display means is concomitantly supplied by the voltage supply generated by the energy means. However, it is also possible to configure the display means in such a way that it requires an external voltage supply. In this case, with autonomous operation of the electronic circuit, before the reading of the display means, an external voltage supply must first be connected. If the electronic circuit has an external voltage supply anyway, for example in the case of the above-described area of use of fail-safe circuits, such an external connection will generally not be necessary.
In order to keep the energy consumption of the display means as low as possible, an LCD display will preferably display the information. However, it is also possible to use other displays if they have a sufficiently low energy consumption. In order to ensure a coordinated transfer of information contained in the ferroelectric capacitors of the ferroelectric flip-flops to the logic gates of the ferroelectric flip-flop, the switch-on control signal preferably has the following signals:
an activation signal for activating precharge transistors of the at least one ferroelectric flip-flop; a transfer signal for transferring the information contained in ferroelectric capacitors of the at least one ferroelectric flip-flop onto internal data lines of the at least one ferroelectric flip-flop; and a current switching signal for switching on the voltage supply of the signal processing means.
In order to ensure that the information contained in the at least one ferroelectric flip-flop is written back in the event of a voltage drop, the switch-off control signal preferably has the following signals:
a transfer end signal;
an activation signal for activating precharge transistors of the at least one ferroelectric flip-flop; and
a current switch-off signal for switching off the voltage supply of the signal processing means.
These different signals are transferred from the control means to the signal processing means preferably by virtue of the fact that signal lines for each of the switch-on signals and switch-off signals lead from the control means to the signal processing means. By way of example, moreover, for the transfer signal and the transfer end signal, a common transfer signal line may lead from the control means to the signal processing means, in which case the transfer signal may consist in the application of a voltage to the common transfer signal line and the transfer end signal may consist in the disconnection of the voltage on the common transfer signal line.
Equally, for the current switching signal and current switch-off signal, a common current signal line may lead from the control means to the signal processing means, wherein the current switching signal consists in the application of a voltage to the common current signal line and the current switch-off signal consists in the disconnection of the voltage on the common current signal line.
Since it is generally very easy to realize counting circuits using flip-flops, it is a preferred embodiment of the present invention that the signal processing circuit is a counting circuit for evaluating a plurality of information signals, which arrive successively or simultaneously, by counting the information signals that have arrived. In this case, it is thus possible for one or more information signal lines to be served simultaneously, provided that the circuit is able to do this. What is then involved is an input signal bus.
The counting circuit comprises, for example, a plurality of cascaded edge-controlled ferroelectric flip-flops, in which the at least one information signal is input into the clock input of the first ferroelectric flip-flop of the plurality of cascaded ferroelectric flip-flops and the output of each of the ferroelectric flip-flops, except for the last, is in each case also connected to the clock input of the ferroelectric flip-flop connected downstream.
What is thus involved in this case is a customary counter circuit arrangement of flip-flops in which, however, ferroelectric flip-flops are used instead of the conventionally used flip-flops.
The invention is also directed at a method for storing information contained in information signals. With regard to the advantages, effects and actions of the method, the statements made above are hereby incorporated by reference in their entirety.
The invention is also directed at a method for storing information represented by at least one information signal or information obtained through evaluation of the at least one information signal in at least one ferroelectric flip-flop in a signal processing means, having the following steps:
A: generating at least one switch-on control signal from an information signal that has arrived, and generating a voltage supply from energy contained in the at least one information signal;
B: activating the signal processing means by the switch-on control signal and applying the voltage supply to the signal processing means;
C: storing an information item represented by the at least one information signal and/or evaluating an information item represented by the at least one information signal and storing the secondary information obtained through the evaluation by means of at least one ferroelectric flip-flop;
D: generating a switch-off control signal after a predetermined time has elapsed after the at least one information signal arrives and/or when the energy converted from the at least one information signal is exhausted; and
E: deactivating the signal processing means by the switch-off control signal.
Therefore, in the case of the method according to the invention, too, two possibilities are available for determining the instant at which a switch-off control signal is generated, namely, on the one hand, once again the simple measurement of a time that has elapsed after the arrival of an information signal, and, on the other hand, the measurement of the energy that is still available and has been obtained from the information signal. This last can be determined, for example, by means of a voltage drop. In this case, too, it is understood that, in the event of the successive arrival of a plurality of information signals, it is desirable for the method not to have the result that, independently of the arrival of further information signals, in a manner governed by the switch-off, these can no longer be detected. Rather, care should be taken in this case, too, to ensure that the time that has elapsed since the last information signal that arrived is measured in each case and that the time measurement starts anew when a new information signal arrives.
In the sense of the method according to the invention, deactivation of the signal processing means is in this case to be understood to mean that the switching-logic states contained in the ferroelectric flip-flops are written back to the ferroelectric capacitors in a controlled manner in order to have the content reliably stored in the event of the final disconnection of the voltage supply.
Step B of the method according to the invention may preferably have the following sub-steps:
B1: activating precharge transistors of the at least one ferroelectric flip-flop by applying a voltage;
B2: deactivating the precharge transistors of the at least one ferroelectric flip-flop by disconnecting the voltage;
B3: applying a voltage to ferroelectric capacitors of the at least one ferroelectric flip-flop for transferring the information stored in the ferroelectric capacitors to logic gates of the at least one ferroelectric flip-flop; and
B4: activating the voltage supply of the logic gates of the at least one ferroelectric flip-flop.
By this sequence of signals which are based on voltage changes, a reliable transfer of the information already stored beforehand to the logic gates of the ferroelectric flip-flop is achieved.
It is also the case in the context of the disconnection of the signal processing means that a specific order of steps is preferably adhered to. Therefore, step E may preferably have the following sub-steps:
E1: disconnecting a voltage present across ferroelectric capacitors of the at least one ferroelectric flip-flop;
E2: deactivating the voltage supply of the logic gates of the at least one ferroelectric flip-flop;
E3: activating precharge transistors of the at least one ferroelectric flip-flop by applying a voltage; and
E4: deactivating the precharge transistors of the at least one ferroelectric flip-flop by disconnecting the voltage.
By virtue of these steps, the opposite process is carried out, in which the levels present at the logic gates are written back to the ferroelectric capacitors as information to be stored.
Preferably, the electronic circuit contains a plurality of ferroelectric flip-flops, wherein the evaluation in step C comprises a summation of the value represented by the information signal and a value already stored in the ferroelectric flip-flops.
Preferably, the summation is effected by means of a counting operation in which the plurality of ferroelectric flip-flops are cascaded in a counter arrangement and an arriving information signal increments or decrements a counter reading of the counter arrangement by the value 1.
Such incrementing or decrementing by the value 1 is appropriate, of course, only if there is merely one input for an information signal. If it is possible for a plurality of information signals to arrive simultaneously or successively via different inputs, the value must be incremented or decremented accordingly.
By way of example, the information stored in the at least one ferroelectric flip-flop can be converted into at least one output signal and be output from the electronic circuit. This additional method step ensures that the information obtained through the information signals can also actually be made available to a user.
The invention is likewise directed at the use of ferroelectric flip-flops. With regard to the effects, advantages and actions of such a use, the statements made above are hereby incorporated by reference in their entirety.
The invention is accordingly directed at the use of ferroelectric flip-flops for electronic circuits, wherein the electronic circuit can detect and/or evaluate information signals and results of the detection and/or evaluation can be stored in at least one ferroelectric flip-flop, this use being characterized in that the entire energy required for the detection, processing and storage can be generated from the information signal.
In this case, the evaluation may comprise counting the arriving information signals. In this case, the electronic circuit can count up or count down the arriving information signals.
Particular preference is attached to a use which is characterized in that the electronic circuit is used in a liquid counter. In the present invention, a liquid counter is understood to be a device which is able to determine the flow of a liquid thorough a cross section, for example a pipe or a channel, and to add up the total quantity of liquid which has flowed through the cross section starting from a start instant. Liquid counters often have to remain at the installation site for long periods of time without being able to be provided with an external power supply. Thus, this is a particularly interesting application example for the present invention, since previous electrical liquid counters require batteries to be exchanged.
Accordingly, the invention is finally also directed at a liquid counter for determining the flow of liquids through a system, having: a sensor which can generate or generates information signals depending on a quantity of liquid flowing through the system; and an electronic circuit which is constructed according to the invention and serves for counting the information signals generated by the sensor; wherein the information signals are the sole energy source for the electronic circuit.